Roofing material



Patented Apr. 23, 1940 UNITED STATES PATENT OFFICE No Drawing.Application August 27, 1936,

Serial No. 98,229

8 Claims.

This invention relates to new and useful improvements in that type ofgranular material which is largely used as a surfacing for asphaltroofing, whether in shingle, roll, or other form, for the purpose ofimparting the desired color thereto and for protective purposes. In themanufacture of such roofing, it is customary to use granules of aparticular color in order that the same may harmonize with a particularcolor scheme. For this reason, granules of various colors must beproduced.

Generally speaking, these granules, known to the trade as roofinggranules have been produced by crushing mineral matter in its naturalstate or otherwise so as to reduce the same to particles of the desiredsize or sizes and by then screening the crushed material so as torecover the said desired size or sizes-from other sizes, after which thesurfaces of the granules thus recovered have been given the desiredcolor by any one of a number of different methods. Coloring methods thathave been employed in the past have been objectionable for variousreasons, however. For example, some have produced colors .that were notpermanent because of being superficially applied and, therefore, notweather resistant, also subject to wear during shipment and handling. Toovercome this objection, roofing granules have been given a glassy orvitreous coating in which a coloring agent has been embedded. Themanufacture of such granules is not only very costly but the coating ishighly frangible as the result of which it has atendency to chip ofiwhile the granules are in shipment and also while they are being handledby the roofing manufacturers. This chipping not only produces sharprazor-like edges on the granules, which are injurious to the hands andclothing of persons handling the roofing to which such granules havebeen applied, but the chipping also results in an excessive amount offines which are not only too small for use as roofing granules but whichgreatly retard the proper adherence to the asphalt roofing of thegranules in general. For this reason, it is frequently necessary forgranules of this type to be re-screened after delivery to the roofingmanufacturers, resulting in a loss of time and consequent expense. Thisre-screening does not, however, eliminate the highly objectionable sharpedges to which reference has been made.

Instead of applying the coating of colored glassy material tothegranules, as just described, to obtain permanency of color, some haveproduced granules of the present type by first producing a vitreousproduct consisting of a combination of mineral substances and a suitablecoloring agent which have all been fused into a dense vitreous mass ofa'glassy nature and by then crushing and screening this vitreous mass toobtain the desired sizes. Being vitreous or glassy, this mass, like thevitreous coating already mentioned, is exceedingly brittle so that thecrushing operation produces on the resultant granules the sameobjectionable sharp razorlike edges to which reference has already beenmade. Roofing granules produced in this manner are also highly frangibleso that, during shipment to the roofing manufacturer and during handlingby him, particles are chipped therefrom, so that objectionable fines areproduced which are not only unsuitable for use but retard adherence'asalready explained.

To insure color permanency, it is necessary for roofing granules to becolored with a non-fading coloring agent throughout their entire extentand not merely superficially coated therewith. It is also necessary thatthe material of which the granules are made be not too brittle so as toavoid, during the crushing operation, also during shipment and handling,the production of excessive fines and the formation of the sharp edgesalready mentioned.

A further disadvantage common to roofing 1 granules having the smoothglassy surfaces that result from complete vitrification is that, becauseof these glassy surfaces, they do not properly adhere to the asphaltsurface of the roofing in connection with which they are employed.

With the foregoing in view, an object of the present invention is toproduce granular material of the type mentioned which shall be ofweather resisting color throughout.

Another object is to provide a base material to be crushed into granulesof a given size or sizes,

which shall not have been completely vitrified 40 and, therefore, not sobrittle as to produce, either during the crushing operation or duringsubsequent handling, an excessive amount of fines nor to produce sharpedges on the finished granules.

A further object is to provide roofing granules which will properlyadhere to the asphalt surface of bituminous roofing, a characteristicwhich is decidedly lacking in the vitreous granules and vitreous coatedgranules already mentioned.

A still further object is to provide a base material to be crushed intogranules, which base material shall be formed into such shapes as willfacilitate the crushing operation.

1 With the foregoing and other objects in view, 1

I produce granules according to my invention,

broadly speaking, by first producing dense and substantiallynon-absorbent semi-vitreous material of a stony character, to whichmaterial I will hereinafter refer as the base, by sintering togetherfine particles of suitable mineral substances, with or without thecoloring agent, which semi-vitreous base is then crushed and screened toproper size. The term "semi-vitreous does not mean that the compositionhas become a glass, but only that it contains enough of a glassy matrixto fill the interspaces between the mineral particles with fusedmaterial to a sufficient degree to cause the resultant base to be dense,substantially non-absorbent, and of a stony character.

In preparing the base to which I have just referred, I select certainhighly siliceous minerals such as quartz, quartzite, feldspar, shale,slate, clay, epidote, greenstone, etc., two or three of such substancesbeing sufficient as a general rule. although Imay use any numberdesired. One

or more of the mineral substances selected shouldpreferably be fusibleand borax, or other suitable flux, should also be included. Clay, orother mineral equivalent, to produce a plastic mass may also be used. Attimes, minerals may be selected which, when ground, mixed together, andfired will produce a base having the color desired for the finishedgranule, but it is generally necessary to add a suitable coloring agentto the mix in order to obtain the desired colors and shade. When thiscondition obtains, it is well to select, for forming the base, mineralmatter having a minimum amount of color, or having a color which, whenburned, will approach that desired for the finished product, as nearlyas possible.

The mineral matter selected, with or without a coloring agent, is firstdelivered to a suitable pulverizing mill where it is also thoroughlymixed. When the material has been properly crushed, mixed and screened,an amount of water is added to produce a stiff plastic mass. It isimportant to use such an amount of water as to properly control theplasticity of the mass and, when color oxide is used, to suit theparticular type employed. I have found,. in practice, that the followingdry material, used in the proportions stated, give satisfactory resultswhen used as a batch or mix for producing a green base to'be crushed andscreened, it being understood that the amount of color oxide'will dependupon the colors of the remaining portions of the mix:

Pounds Quartz 1300 Borax 40 Clay 500 Feldspar 200 Chromium oxide 16 Itwill be understood that the proportions given may be somewhat varied toobtain best results, and that substitutes for these materials may beemployed. The quartz, which may be in the form of rock or sand, is usedto produce a refractory structure, also for sintering the otheringredients together during the firing process to be explained latertherein. The borax is used as a fiux and the clay is used to impartplasticity to the entire mix and to hold the other ingredients togetheruntil fired. The clay employed may be natural clay, brick clay, kaolin.or any similar mineral substance that will impart to the entire mix theproper degree of plasticity. The feldspar is used to impart a properdegree of hardness and insolubility to the finished granules and thechromium oxide is for coloring, as will die.

be understood. If other ingredients are employed, care must be taken toselect those having the same stated characteristics as those given inthe foregoing formula.

After the ingredients have been properly ground and mixed together, theyare transferred, in any suitable manner, to a pug mill such as is usedin the manufacture of bricks, where a suitable amount of water is addedto obtain the consistency already described. With the formula givenabove, this should be about 40 gallons. The plastic mass thus producedis then transferred to an auger or extruding device from which it isforced through a. suitable forming I have found that a die having acircular passage of about one-half (V an inch in diameter therethroughis satisfactory, as this will cause the plastic material to issue fromthe ex- "truder in cylindrical form and of a convenient size. Otherforming dies may be used, but care should be exercised to select onewhich will cause the plastic material to assume a size which, whenbroken into sections, may be readily fired.

As the cylindrical column of plastic material issues horizontally fromthe die of the extruding device, it breaks, because of gravity, intorelatively short sections which fall onto a conveyor belt placedslightly beneath said die, and are thus carried to a suitable kiln,preferably one of the rotary type, where they are fired at a temperaturesufiiciently high and for a sufficient length of time to causesemi-vitrification only. That is to say, they are fired in such a manneras to cause a sintering together of the mineral particles of which theplastic sections or shapes are formed, but'no t in a manner to reducethe shapes to a molten state, nor even to deform them. The temperatureand time of firing must, in fact, be only sufficient to burn thesections to a dense compact mass. For theformula given herein, thistemperature should be approximately 2000 F., and the firing should becontinued for about 30 minutes.

When the sections of the base have been properly burned, they pass fromthe kiln into a suitable cooler and, when cooled, they are crushed andscreened to proper size according to the use for which they areintended. For use as roofing granules, they should be crushed andscreened to pass an 8 or 10 mesh screen and be retained on a 35 meshscreen. Particles too fine for use may, of course, be used for making asubsequent batch for producing the base. Oversized particles arereturned to the crusher.

In order that the plastic sections of the base may become partiallydehydrated and hardened before they enter the kiln, so as not to becomedeformed therein before they are completely burned, the conveyor beltmay pass through a zone of heat taken from the kiln or from any othersource.

A particular advantage arising from my invention is that granules may beproduced in accordance therewith in most any locality because they maybe made of materials that are to be had in practically any part of thecountry. For this reason, great savings may be effected in the cost ofshipping.

Attention is also called to the fact that the crushing of the basematerial, due to the fact that it is only semi-vitreous, will producegranules having rough or granular faces, thus assuring their properadherence to the asphalt of the roofing in connection with which theyare used. While the material described herein has been mentioned asbeing particularly adapted for use in connection with the manufacture ofbituminous roofing, it is to be understood that it may 1 A compositesheet body for roofing or like purposes comprising a plastic stratum andan adherent surfacing for same consisting of granular material theindividual granules of which are characterized by having a dense bodyconsisting throughout of particles of siliceous mineral matter heldtogether by a partly vitrified matrix, said matrix filling theinterspaces betweensaid particles.

2. A composite sheet body for roofing or like purposes comprising aplastic stratum and an adherent surfacing for same consisting ofgranular material the individual granules of which are characterized byhaving a dense body consisting throughout of particles of siliceousmineral matter held together by a partly vitrified matrix, said matrixincluding a coloring agent and filling the interspaces between saidparticles.

3. A composite sheet body for roofing or like purposes, comprising aplastic stratum and an adherent surfacing for same consisting ofgranular material the individual granules of which are characterized byhaving a dense body consisting throughout of particles .of siliceousmineral matter held together by a partly vitrified matrix comprisingclay and a flux, said matrix filling the interspaces between saidparticles.

4. A composite sheet body for roofing or like purposes, comprising aplastic stratum and an adherent surfacing for same consisting ofgranular material the individual granules of which are characterized byhaving a dense body consisting throughout of particles of siliceousmineral matter held together by a partly vitrified matrix comprisingclay and a flux, said matrix filling the interspaces between saidparticles, and said individual granules having granular faces.

5. A composite sheet body for roofing or like purposes, comprising aplastic stratum and an adherent surfacing for same consisting ofgranular material the individual granules of which are characterized byhaving a dense body consisting throughout of particles of siliceousmineral matter held together by a partly vitrified matrix comprisingclay, a fiux, and a coloring agent, said matrix filling the interspacesbetween said particles, and said individual granules hav ing granularfaces.

6. A composite sheet body for roofing or like purposes, comprising aplastic stratum and an adherent surfacing for same consisting ofgranular material the individual granules of which are characterized byhaving a dense body consisting throughout of particles of siliceousmineral matter held together by a partly vitrified matrix comprisingclay, feldspar, and a flux, said matrix filling the interspaces betweensaid particles.

'7. A composite sheet body for roofing or like purposes comprising aplastic stratum and an adherent surfacing for same consisting ofgranular material the individual granules of which are characterizedbyhaving a dense body consisting throughout of particles of siliceousmineral matter held together by a partly vitrified matrix, said matrixfilling the interspaces between said particles, and each of saidindividual granules comprising approximately 24% of clay and 63% ofquartz mineral.

8. A composite sheet body for roofing or like purposes comprising aplastic stratum and an adherent surfacing for same consisting ofgranular material the individual granules of which are characterized byhaving a dense body consisting throughout of particles of siliceousmineral matter held together by a partly vitrified matrix, said matrixfilling the interspaces between said particles, and each of saidindividual granules comprising approximately 251% of clay, 63% ofquartz, 2% of borax, and 10% of feldspar.

ERNEST H. NICHOLS.

